Yes, the D300 was a particular camera born of the situation Nikon was in. I suspect they felt it necessary to produce a camera to that spec to maintain faith with the DX D2 users, who had been convinced that DX had advantages. So, essentially the D300 is an updated D2X - updated with the D3 AF and the Exmor sensor. It probably costs just as much to build as the D2X - most of the internal mechanisms are the same. In the event, most of the D2 owners moved seamlessly to the D3 and discovered the advantages of full frame. The market for the D300 ended up being wannabe pros who wouldn't shell out for the real thing, plus the real enthusiast amateurs for whom the D200 and 40D/50D had always been the staple.

Very plausible explanation. Makes a lot of sense.

The result was that the D300 was very successful in its early period, and ate the 50D's lunch. Canon's response was the 7D, where they managed very cleverly to get almost all of the marketing kudos of the D300 without the production expense. It had a rocky start due to its AF issues, but once it started motoring, the revenues to Nikon from the D300 must have been very small. Hence, as you say, the D7000.

Well, the 7D followed a very similar sales curve as the D300: it was selling very well in its first year but after the release of the D7000, sales more or less stalled - energized only by periodic discounts.

My feeling is that Nikon (correctly) recognized that the market for an expensive DX/crop body is somewhat limited. Hence, they don't seem to be investing heavily in a D300s replacement.

The thing is, the short buffer on the D7100 actually suggests that we might see a D400 after all. But this D400 will be a D7100-H, actually - that is, a D7100 with less megapixels and higher frame rate. Not a separate model like the D300 was.

As for Canon - they've obviously left room in their lineup for a 7DII.But like you said, the 7D was not expensive to build anyway. So, no big deal to update it and continue selling it, as they can always adjust the price if necessary.

I don't think a lower mega pixel D7100H is what is coming. There would be an even smaller market for that camera than there would for a D400. I think it is more likely we will see a D8000/D9000 that is basically a D7100 but with a larger buffer, 7-8 FPS, 91K pixel meter, and maybe an AF on and D800 style buttons on the top left instead of the D7100's mode dial. Well actually I think it is far more likely we won't see any other DX camera because the D7100 it the new top model and Nikon is holding back the larger buffer for the D7200.